Interpretive Summary: Carbaryl-bran bait is an effective control commonly used against grasshoppers. Bran bait doesn't kill or harm as many non-target organisms as do liquid sprays, but ground beetles may be susceptible to these baits. Ground beetles are beneficial insects as predators of insect pests and weed seeds. Although Alaska has fewer species of invasive weeds than other areas in the continental U. S., the weed flora in Alaska has been steadily growing. Ground beetles and their consumption of weed seeds has not been previously studied in agricultural settings in Alaska. This study examined the effect of grasshopper bran bait on ground beetle populations, as measured by pitfall traps, and subsequent predation of seeds of three species of weeds on fields enrolled in the Conservation Reserve Program. Ten different species of ground beetle accounted for over 95% of all ground beetles captured. Bait applications reduced ground beetle populations in each of two years of bait applications. Seed predation was generally low overall and not strongly affected by the bait application, but predation of lambsquarters seed was lower on treated plots in one year. Predation of dandelion seeds was correlated with ground beetles in one year, and predation of dragonhead mint seed in the other year. We conclude that applications of carbaryl bran bait for control of grasshoppers will have only a small, temporary effect of increasing the seed bank of some weeds in high-latitude agricultural ecosystems.

Technical Abstract:
Carbaryl-bran bait is effective against grasshoppers without many impacts on non-target organisms, but ground beetles (Coleoptera: Carabidae) may be susceptible to these baits. Carabids are beneficial in agricultural settings as predators of insect pests and weed seeds. Carabid species composition and their consumption of weed seeds has not been previously studied in agricultural settings in Alaska. This study examined the effect of grasshopper bran bait on carabid activity-density, as measured by pitfall trap catch, and subsequent predation of seeds of three species of weed. Bait applications reduced ground beetle activity-density in each of two years of bait applications. Seed predation was generally low overall and not strongly affected by the bait application, but predation of lambsquarters seed was lower on treated plots in one year. Predation of dandelion seeds was correlated with ground beetle activity-density in one year, and predation of dragonhead mint seed in the other year. We conclude that applications of carbaryl bran bait for control of grasshoppers will have only a small, temporary effect on weed seed populations in high-latitude agricultural ecosystems.